ath9k: Use mac80211 for multicast power save buffering

Replace the internal ath9k implementation of multicast/broadcast frame
power save buffering (AP mode) in ath9k with use of mac80211
ieee80211_get_buffered_bc() mechanism. This removes quite a bit of
duplicated functionality and simplifies the driver part.

Signed-off-by: Jouni Malinen <jouni.malinen@atheros.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
diff --git a/drivers/net/wireless/ath9k/main.c b/drivers/net/wireless/ath9k/main.c
index 55f4868..dca00c3 100644
--- a/drivers/net/wireless/ath9k/main.c
+++ b/drivers/net/wireless/ath9k/main.c
@@ -1362,6 +1362,7 @@
 	}
 
 	hw->flags = IEEE80211_HW_RX_INCLUDES_FCS |
+		IEEE80211_HW_HOST_BROADCAST_PS_BUFFERING |
 		IEEE80211_HW_SIGNAL_DBM |
 		IEEE80211_HW_NOISE_DBM;